Third Arc Bio Announces $52M Series A Extension to Expand Oncology and Immunology & Inflammation Portfolio

$52M equity adds to previously announced $165M Series A

New investor Andreessen Horowitz (a16z) leads the financing with founding investor Omega Funds; additional investors include Life Sciences at Goldman Sachs Alternatives, BVF Partners LP, funds managed by abrdn. Inc., accounts advised by T. Rowe Price Associates, Inc., Marshall Wace, Hillhouse Investment, Galapagos NV, AbbVie Ventures, and Alderline Group

SPRING HOUSE, Pa., Feb. 4, 2026 /PRNewswire/ — Third Arc Bio Inc., a clinical stage biotech company developing novel multifunctional antibodies for a range of oncology and immunology & inflammation (I&I) indications, today announced the closing of a $52 million Series A extension.

New investor Andreessen Horowitz (a16z) joined Third Arc Bio’s existing world-class investor syndicate to further validate the company’s approach to deliver transformational therapies for patients. As part of the financing, a16z General Partner, Jorge Conde, joins Third Arc Bio’s Board of Directors. Proceeds from the financing will enable Third Arc Bio to accelerate its I&I portfolio and deliver additional oncology programs into the clinic.

“Third Arc represents a shift toward more precise immune modulation—moving beyond systemic exposure to therapies designed to deliver highly controlled biological effects at sites of disease,” said Jorge Conde, General Partner at a16z. “The company’s platforms, combined with a team that has repeatedly translated complex immunology into approved medicines, reflect a rigorous, patient-driven approach to building biologics that can improve both efficacy and safety across oncology and immune-mediated disease.”

Since its launch in 2022 with seed financing from Omega Funds, Third Arc Bio has assembled a highly experienced team with a proven track record of drug discovery and development, alongside an innovative platform and a pipeline of multispecific antibodies. The company’s lead asset, ARC101, is a bispecific T cell engager targeting CLDN6 currently in Phase 1 dose escalation in patients with advanced solid tumors.

“This financing allows us to maintain momentum across our expanding oncology portfolio while rapidly advancing our next-generation I&I assets into first-in-human studies,” said Peter F. Lebowitz, MD, PhD, Chief Executive Officer of Third Arc Bio. “By parallel-tracking programs, we can more efficiently validate the full potential of our platforms, rapidly generate proof-of-concept data, and deliver innovative therapies for patients with significant unmet need.”

Third Arc Bio’s approach to I&I is anchored by its ARCTag (Tethered Agonist) Platform, which leverages multispecific antibodies to localize immune modulation directly to sites of disease. This targeted activity represents a meaningful advance beyond conventional systemic autoimmune therapies, offering the potential for enhanced efficacy and therapeutic index.

About Third Arc Bio
Third Arc Bio is a clinical stage biotech company developing multifunctional antibodies that generate immune synapses to precisely activate or inhibit T cells. The lead program ARC101, is a bispecific T cell engager currently being evaluated in a Phase 1 trial for cancer patients with solid tumors expressing CLDN6. The company’s drug development engine delivers superior biologics optimized to create best-in-class T cell engagement by leveraging novel technologies that power a pipeline of high value therapeutics. The Third Arc Bio platforms include a solid tumor ARCStim Platform and an immunology & inflammation (I&I) ARCTag Platform that offers precision immune regulation to achieve superior efficacy and safety. To learn more, visit www.thirdarcbio.com.

Media Contact
Peg Rusconi, Deerfield Group
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SOURCE Third Arc Bio